Which carbs do I want for 2x4 MR?

[elmariachi]

I have pinged a couple of you offline but I want to open this up for broader feedback. I recently found a practially new original Ford 2x4 MR intake. At some point later, not sure when, I might like to run it (in lieu of the Sidewinder/750 Demon I am running now.)

My engine is not a wild setup, 1966 side oiler, stock MR heads, Comp 294S flat tappet (248/248, .605 lift) 9.8:1 compression. It would seem to me the original 700+ cfms would be too much for street and a some weekends at the track. I have read a lot here about people trying to decide between 390s, 450s and 600s, but no one ever seems to come back and actually post how they are doing months later. If anyone can comment on your experiences and what cfm/list #s you'd recommend I would appreciate it.

Jim

[patrickt]

[elmariachi]

That would be the one:

[FWB]

use the 700's, they are avail from carl's ford parts they were what the factory put on the 427 street cars. jetted properly the vacuum secondary carbs offer great drivability with good performance when needed.



http://www.carlsfordparts.com/main.html

[sideoiler10]

I am running two 600 cfm Holley carbs. that I got from Carl's Ford Parts. I am running them on a low riser manifold, but for you, since you have the MR heads I would recommend using a MR 2x4 intake. The 2x4 Tunnel Wedge would be my recommendation if it will allow the carbs to fin under your hood and scoop. Mine barely clear.

I had absolutely no problems at all with the new carbs from Carl's Ford Parts. He sells new sets of BK and BJ carbs that have been run-in. The only adjustments we had to make were the idle speed and the idle jets a little. Of course we had to installe the 2x4 linkage, also available from Carl.

Performance is awesome. You can adjust the linkage to bring the second carb in as soon as you need it. If you sort of double pump the throttle and really hammer it the secone time it will almost rip your head off.

Honestly though, a single larger 4 barrel with a good intake like a sidewinder, will probably give better acceleration, somewhat better. But, the slight difference is more than offset by the WOW facter of the dual quads. The only thing better is a set of webers poking up at you.

Good luck whichever way you choose. Bob

[elmariachi]

Thanks Bob, this is an MR intake that I have purchased, and my heads are stock MR, for now. Are the 600s you mention the "1850s"?

[blykins]

I would run a pair of Quickfuel Holley 1850 clones. Probably 2 650's.

[sideoiler10]

Yes they are the 1850s. They are the same ones Ford put on the 427's and the first dual quad 428s. Some of the 427s may have had 710s or 750s. I would have to check my book to be sure.

[undy]

The 428 cars and the Shelby 428 Mustangs were running the BJ BK carbs which were 600 CFM. They were not 1850s, there were differences. The 427 Cobras, Galaxies and Fairlanes got the BC BD Carbs which were 710s.

[patrickt]

[elmariachi]

Originally Posted by undy

The 428 cars and the Shelby 428 Mustangs were running the BJ BK carbs which were 600 CFM. They were not 1850s, there were differences. The 427 Cobras, Galaxies and Fairlanes got the BC BD Carbs which were 710s.

IIRC, they were the BJ/BK List 2840 and 2850, maybe someone can confirm.

[patrickt]

[lineslinger]

Twin 750's on Dove med. riser intake.

[undy]

My set of custom built, Survival Motorsport sourced, Quick fuel 750s. They have a custom secondary metering plate with replaceable jetting and a host of other mods..



Dave

[601HP]

Knowing what I do now, I would purchase the Holley BJ/BK set from Carl's, or Survival Motorsports' similar set-up. Those carbs are far better matched throughout their operating range, than bolting on a pair of Holley 600's as I did years ago.

My original pair of 600's always ran too rich because of; the air bleeds (idle and high speed), transition circuit, and other tweakings needed. This wasn't a poor combination, but it could have been better. I've been told the 600 was essentially designed to be run as a single carb application, and when used in a dual configuration, fuel distribution in certain portions of the operating band result in a rich condition. I subsequently found that to be true, in my application.

Just this year a fellow Cobra owner shared a lot of carb tuning data with me that he put together through extensive wide-band tuning efforts, various sensors mounted on his engine, and documented it all via a laptop. He also spent considerable time on the internet gleaning info from other sources. I copied his efforts, and spent a lot of hours modifying, tapping, drilling, adjusting and tuning my 600's. I made some additional changes to my setup that helped further tweak my engine. The engine runs noticeably cleaner, and driveability has been enhanced especially between off-idle and 3,000 rpm.

I enjoy fiddling with things as I described above. Some folks may not want to invest the effort I did, and would rather bolt-on multiple carbs that are nearly ready to be driven. My efforts to modify the 600's would probably not be necessary if the BJ/BK's were used instead of the 600 cfm 1850's.

David

[ERA Chas]

Originally Posted by undy

My set of custom built, Survival Motorsport sourced, Quick fuel 750s. They have a custom secondary metering plate with replaceable jetting and a host of other mods..
Dave

Dave,
Barry's set up is great but you are killing a lot of the 1500CFM with that air cleaner. Acts like a rev limiter.

[mr0077]

El, I never tried the 450 CFM Holleys or the BJ/BK carbs from Carl's, but I tried the 390's and the 600's. Both were easy to tune, with the 600's making about 15 more HP on the wheel dyno and the 390's being the most responsive and a little more user-friendly on the street.

If I could do it over, I would spend the extra $550 for the BJ/BK set, and end up saving some money. Don't know of anyone that tried the 600's and didn't like the BJ/BK's better.

[undy]

Originally Posted by ERA Chas

Dave,
Barry's set up is great but you are killing a lot of the 1500CFM with that air cleaner. Acts like a rev limiter.

Yea, I know .... unfortunately there's just no more hood room available for a taller filter. I'm already paranoid of renegade raised man-hole covers

Believe it or not it only lost 15 rwhp at peak over no filter at all.

[trularin]

Pat, you have way too many pictures you can pull out to prove a point!



I like that first Swiss cheese to foundry ad.

[patrickt]

Originally Posted by trularin

Pat, you have way too many pictures you can pull out to prove a point!

It helps offset my inability to convey simple concepts with written prose....